Glad you asked, because there's a bit of confusion on the topic. While James's gowns adhere to the techniques and artistry of couture, he was never formally educated in design. Requirements from the Paris Chamber of Commerce demand technical training at the Ecole de la Chambre Syndicale de la Couture Parisienne. So while he worked in the tradition of haute couture, his gowns, in fact, are not couture.
Source: The Metropolitan Museum of Art